Patent GB-481520-A (GB)
Abstract: 481,520. Photographic roller blind shutters. LEITZ GES., E. Sept. 11, 1936, No. 24835. Convention date, Sept. 30, 1935. [Class 98 (i)] A focal plane shutter includes a cam set from outside by an exposure setting member, a device operated from outside the camera for releasing the first blind, means for releasing the catch of the second blind and comprising a doubly pivoted arm which changes its centre of rotation upon engagement with the setting cam, and a locking member for time exposures which is brought into operation by movement of the exposure setting member. The shutter blinds A, B are connected respectively at one end to bands A<1>, B<2> wound on coaxial drums A<2>, B<1>, and at the other end to drums A<3>, B3 containing adjustable tension springs A<4>, B4. The spindle AS supporting the winding drums A<2>, B<1> carries a cam A<9> at its upper end. A sleeve B<9> is loosely mounted on the spindle A<8> and is connected to the drum B<1> by a pin B<8> passing through an almost arcuate slot A<10> in the drum A<2>. A locking finger B<10> and a braking finger B<11> are mounted on the sleeve B<9>. The spindle A<8> is journalled at its upper end onto a stub shaft D which carries a rack and spring setting knob D<1>, a a setting cam D<2>, a further cam D3, and a cam D<4> for setting the resistance of an exposure meter. A roller E<1> and pin E<2> both on a lever E, engage respectively with the cams A<9>, D<2>, the lever being pivoted at E<3> to a catch arm F. The roller E<1> is pressed onto the cam A<9> by a spring E4 coiled round a pin C<5>. The catch arm F is carried by a sleeve F<1>, and is freely rotatable on a vertical rod G and within the walls C, C<2> of the camera. A nose F<2> on the catch arm F engages with the locking finger B<10> to lock the second blind against movement. The arm F moves between stops C<3>, C'. A vertical rod G carries a collar G<1> at its lower end and is acted upon by two spring blades G<2>, G<3>, the former being the weaker. A locking arm G<4> on the upper end of the rod G is guided on a fixed pin G<6>, and a projection G5 is interposed in the path of a finger F<3> on the sleeve F<1> when the rod G is moved downwardly. A pin G<7> extends down from .the arm G<4> and has a projection G<8> which normally lies on a level with the braking finger B". This finger B<11> co-operates with an arm H<1> on a spindle H, which is journalled at its upper end in one arm J of a pivoted lever J, J<1>. A spring J<3> urges the arm J<1> into engagement with the upper cam D<3>. The lower end of the spindle H carries a forked arm which engages with a pin and escapement mechanism. The lower end of the spindle H rests on a spring blade H<5> which is raised by a cam and disc arrangement on the spindle A<8> just before the end of the running down of the first blind, whereby the arm H<1> is brought up to the level of the braking finger B". A spindle K is connected through a clutch K<2> and gearing K<1> to the spindle A<8>, by which the blinds are wound up. A release knob K<3> when depressed, disengages the clutch K<2> against the action of the spring G<3> and releases the first blind. The setting knob D<1> can be moved to four distinct positions corresponding to exposures as follows:- (1) Short instantaneous exposures. A point on the cam D<2> between the points D<7>, D<8> lies opposite the pin E<2>. When the release knob K<3> is depressed, the first blind A is released and the spring G<2> tends to move the rod G downwardly, the pin G<6> striking the cam D<2> and preventing this movement. As the cam A<9> rotates, the roller E<1> which is pressed against it, moves inwardly until the pin E2 strikes the cam D<2>. The centre of rotation of the lever E then changes to E<2> and an outward movement of the pivot E<3> results. The nose F<2> is consequently swung away from the locking finger B<10> and the second blind B is released. The slit width depends on the position of the setting cam D<2>. (2) Long instantaneous exposures. The pin E<2> lies opposite a point between the points D<9>, D<10> on the setting cam, and in this position, before the pin E<2> strikes the cam, the first blind will nearly have completed its running- down and the spring blade H<5> will have raised the spindle H. This interposes the arm H<1> in the path of the braking finger, and when the second blind is released by the catch nose F<2>, its motion is impeded by the escapement mechanism. The time of full release depends therefore on the position of the arm H<1> which is determined by the cam D<3>. (3) Brief time exposures. The setting knob D<1> is moved to bring the pin G<6> above a recess D<6> in the cam D<2>, thus permitting downward movement of the rod G. Upon depression of the release knob K<3>, the projection G<5> is moved into the path of the finger F<3> preventing rotation of the catch arm F. The second blind thus remains locked until the knob K<3> is released to return under the action of the spring G<3> and release the finger F<3>, whereupon the blind runs down. In this setting, the arm H<1> is out of the path of the finger B<11>. (4) Long time exposures. The pin G<6> lies above a hole D<5> in the cam D<2> permitting downward movement of the spindle G. The arm J<1> is moved by the cam D<3> so that the arm H<1> lies beneath the path of the braking finger B". When the release knob is depressed, the first blinds A runs down, and the projection G<5> locks the arm F. When the knob is released, the locking finger B<10> is released by the movement of the projection G<5> on the rod G, but the second blind is then held by the braking finger B<11>. When the knob K<3> is again depressed, the rod G moves down and the arm H<1> is then free to rotate and liberate the second blind. In a modification, Fig. 12, the sleeve F<1> of the catch arm F surrounds a spindle L which carries a locking arm L<4>. The arm L<4> slides on a pin F<4> on the locking finger F<5> and has a projection L<6> which fits in a slot D<12> in the disc D' of the setting knob. A projection D<11> on the setting shaft D lies normally below the end L<5> of the arm L4. In making a time exposure, the spindle L is lowered, so that the projection D<11> prevents movement of the catch arm F. When the knob K<3> is released, the end L<5> is disengaged and, moving into the slot D<12>, permits the second blind to be released. For instantaneous exposures, the projection L is forced out of the slot D<12>, and exerting a pressure on the spring at the bottom of the spindle relieves the pressure on the release spindle K.